In the operation of a machine tool, such as a boring machine, it is often necessary to generate a non-cylindrical surface of revolution such as a sphere. This would be true if one were manufacturing the movable element of a ball valve, for instance. In the past, the necessary relative movement between the workpiece and the tool has been brought about by the use of a mechanical template or cam. Another method of accomplishing this purpose is by use of a numerically controlled machine tool, wherein the relative feed motions are brought about in accordance with a signal introduced into the machine from a punched tape or the like. Machine tools that use either the mechanical template or the numerical control method are unwieldy and very expensive. Furthermore, it is difficult to convert from one pattern to another without encountering considerable set-up time. The accuracy of the template method, of course, is tied in with the accuracy of formation of the template; this means that the template is not only expensive, but, when it wears, the form deteriorates. These and other difficulties experienced with the prior art devices have been obviated in a novel manner by the present invention.
It is, therefore, an outstanding object of the invention to provide a machine tool having means for producing accurately and quickly a non-cylindrical surface of revolution.
Another object of this invention is the provision of a machine tool for producing a surface of revolution of curved shape without the use of a mechanical template or of a numerically controlled feed mechanism.
A further object of the present invention is the provision of a machine tool for producing a non-cylindrical surface of revolution, which machine is inexpensive to manufacture and which may be readily operated without difficulty by an ordinary skilled machinist.
With these and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set forth in the specification and covered by the claims appended hereto.